Jack Russells are sturdy and tough, measuring between 10" and 15" at the shoulder. The body length must be in proportion to the height, and the dog should present a compact, balanced image.
The Jack Russell should always appear balanced and alert, As the Jack Russell is primarily a working terrier, their most important physical characteristic is their chest size, which must not be so large that it prevents the dog from entering and working in burrows. The red fox is the traditional quarry of the Jack Russell Terrier (JRT) so the working Jack Russell must be small enough to pursue its quarry. Red foxes vary in size, but across the world they average about 14 pounds in weight and have an average chest size of 12-14 inches at the widest part.
Jack Russells are first and foremost a working terrier. Originally bred to bolt fox from their dens during hunts, they are used on numerous ground-dwelling quarry such as groundhog, badger, and red and grey fox . The working JRT is required to locate quarry in the earth, and then either bolt or hold it in place until they are dug to. To accomplish this the dog must bark and work the quarry continuously. Because the preservation of this working ability is of highest importance to most registered JRTCA/JRTCGB breeders.
Jack Russells tend to be extremely intelligent, athletic, fearless, and vocal dogs. It is not uncommon for these dogs to become moody or destructive if they are not properly stimulated and exercised as they have a tendency to bore easily and will often create their own fun when left alone to entertain themselves. Their high energy and drive make these dogs ideally suited to a number of different dog sports such as flyball or agility. Obedience classes are also recommended to potential owners as Jack Russells can be stubborn at times and aggressive towards other animals and humans if not properly socialized (a process that should be continued throughout their whole lives). Despite their small size, these dogs are not recommended for the condominium or apartment dweller unless the owner is ready to take on the daunting task of providing the dog with the necessary amount of exercise and stimulation.
These are truly big dogs in small packages, which can sometimes lead to trouble involving larger animals. The JRT owner must be aware of these tendencies and keep an eye out for trouble in many situations. - - Jack Russell terriers are not recommended for families with young children as they are intolerant of even unintentional abuse and will often return a perceived injustice with aggression. This is not to say that the Jack Russell can not cohabit with well behaved children but both dog and child need to be properly introduced and educated on how to behave towards one another, and never left unsupervised.
Despite some of these negative traits JRTs are exceptionally loving, intelligent dogs who have the ability to entertain their owners for hours with their comical antics. Www.jack-russell-pictures.com describes the JRT well: "To understand the Jack Russell temperament, it must be remembered that they are first and foremost a "working dog". In other words, they were designed to aggressively run, chase, and flush out fox and badgers in the great hunts of England. These traits, so passionately guarded by Jack Russell breeders since the 19th century, have delivered to us a dog that is fearless, happy, alert, confident, intelligent and lively. A dog that is ready to meet the world on a moment's notice...this is the Jack Russell temperament in a nutshell."
Health:
Jack Russell terriers are known for longevity and health due in a large part to a large gene pool. The JRTCA specifically regulates inbreeding and line breeding to a 16% coefficient unlike many of the kennel club show dog breeds. A well-cared-for Jack Russell can live well into its teens, remaining active right into its senior years. The typical lifespan is between 12 and 19 years.
Health concerns with the breed include hereditary cataracts, primary lens luxation, congenital deafness, medial patellar luxation, cerebellar ataxia, Legg-Calve-Perthes Disease, myasthenia gravis, atopy, general joint problems, and von Willebrand's disease. Responsible breeders have breeding stock BAER tested for hearing as juveniles and CERF (Canine Eye Registry Foundation) tested annually to check for any hereditary defects. Although not commonly a problem in this breed, some breeders choose to have their dogs OFA inspected for potential joint problems.
